The Spanish word 'edredón', meaning 'eiderdown' or 'duvet', comes to Spanish through French 'édredon', which in turn was borrowed from German 'Eiderdaun'. The German word refers to the soft, warm down feathers of the eider duck, which were historically prized for making warm bedding. This etymology reflects the historical luxury trade in eider down across Europe, with the term originating in Germanic languages and spreading to Romance languages like French and Spanish.

There aren't many common Spanish words that are etymologically related to 'edredón', as it's a relatively recent borrowing from French and stands somewhat isolated in Spanish vocabulary.

English speakers might recognize this word's connection to 'eiderdown', which refers to the same thing - the down feathers of the eider duck or a quilt stuffed with these feathers. The English word comes from the same Germanic source as the German 'Eiderdaun', combining 'eider' (the type of duck) and 'down' (soft feathers). This makes it easy to remember that Spanish 'edredón' refers to this type of warm, soft bedding.